If PDF is electronic paper, then pdftk is an electronic staple-remover, hole-punch, binder, secret-decoder-ring, and X-Ray-glasses. Pdftk is a command-line tool for doing everyday things with PDF documents. Keep one in the top drawer of your desktop and use it to: Merge PDF documents, split PDF documents, apply watermark, repair corrupt PDF, update PDF metadata and much more. pdftk does not require Acrobat and is free software (GPL) pdftk requires java.